Sky & Telescope - November 2020 - 67

adjustments during polar alignment - a
somewhat tedious job in the dark. There
is a nice storage slot for the hex wrench
just above one of these bolts, but knobs
or some other tool-free solution instead
of the hex bolts would be more convenient. The wrench performs double
duty since it can be inserted into holes
around the edge of the small knurled
wheel that adjusts the altitude axis during polar alignment. This knurled wheel
is tucked under the polar axis and is
tough to grab with just your thumb and
foreﬁnger, so inserting the wrench adds
greater leverage. GEM45 has a generous
latitude range of 14° to 68°.
The mount includes iOptron's
new Universal Self-Centering Saddle,
which accepts both Vixen-style and
the wider Losmandy-style dovetail
mounting plates. To swap between the
two formats, users disconnect the two
jaws with the onboard hex wrench and
reattach them upside-down. Two of the
four mounting screws on the stationary
clamp are shorter than the other two,
so be sure to note where each goes. The
Losmandy-style setting also includes an
alignment scale to help accommodate
narrower dovetail plates.
The two saddle clamping knobs are
1 inch wide but protrude less than an

p iOptron's Universal Self-Centering Saddle
accepts both Losmandy- and Vixen-style
dovetail mounting plates. Users remove the
clamps and replace them upside-down to
switch between formats. The back end of the
saddle includes passthrough ports for USB 2.0
accessories and an ST-4 standard autoguider.
The center-positive barrel connector power
jack typically requires a male-to-male cord to
power a camera or other accessory.

inch from the saddle jaws, making it
difﬁcult to get a solid grip on them. The
center of each knob accepts a 5-mm
hex wrench. Once, while mounting
my 8-inch Ritchey-Chrétien OTA, the
mounting bar slipped in the saddle due

q Connecting the GEM45 equatorial head to the tripod base requires the
included 4-mm hex wrench to tighten down the two cap screws, which
also double as the azimuth lockdown mechanism. The hex wrench can
also be used to adjust the altitude of the mount by inserting it into the
holes on the knurled knob at right.

A LL PHOTOS BY THE AU THOR

q Unlike with other iOptron mounts, the center post is not threaded
to attach the GEM45 head. Instead, the center post is merely a pivot
point, and the mount is secured using two of the threaded holes on the
tripod head. The azimuth adjustment pin can be moved to any of the
four threaded holes to ensure the counterweight shaft does not strike the
tripod legs when using the mount at low latitudes.

to insufﬁciently tightening the knobs.
A stop screw on the bar prevented any
damage, but afterwards I always used
a 5-mm hex wrench to make sure the
saddle jaws were sufﬁciently tight.
The Universal Self-Centering Saddle
works well, though it places telescopes
farther from the center of the polar
axis, which means you may need more
counterweights than typically required.
For example, when using a heavy SCT
with a diagonal and eyepiece weighing
32 pounds, it required 40 pounds of
counterweights to balance.
While the hex-head bolts and the
lack of sizeable clamping knobs are
minor inconveniences when assembling the GEM45, the mount does
have several convenience features. The
counterweight included with the mount
has compression rings rather than a
lock-down screw to prevent marring the
counterweight shaft.
The lower end of the saddle plate has
its own 12 VDC output power jack, a
port that accepts an ST-4-compatible
autoguider cable, as well as a USB
2.0 passthrough socket. (The input is
located on the rear of the RA axis.) I
routinely used these ports to power my
camera's cooler and connect my autoguider. Conﬁgured in this way, all these

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67
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Sky & Telescope - November 2020

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